What Is Code Smell And How To Reduce It?

In today’s digital world, when having good and reliable software plays a crucial role in the operational processes of every business, the developers bear the responsibility to produce high-quality code. However, that’s easier said than done. They may encounter various challenges during the development process that can lead to unintentional mistakes, resulting in what is known as code smells. But what is code smell

What Is Code Smell And How To Reduce It?

Let’s explore this concept in more detail.

What are code smells? 

Back in the late 1990s, Kent Beck, the creator of extreme programming, emphasized the importance of design quality in software development. He played a significant role in popularizing the term “code smell” to describe certain patterns or characteristics in code that indicate potential issues or weaknesses.

Just like a foul odor from the fridge suggests the presence of something unpleasant, a bad code smell suggests the presence of poor design or implementation choices. Thus, these “smells” are not bugs or errors in the traditional sense. They are not technically incorrect and do not currently prevent the program from functioning. It’s like a red flag waving to grab the attention of developers and prompt them to investigate further. 

However, it’s important to note that not all code smells necessarily indicate a problem. Some may be harmless or even intentional design choices. Therefore, it’s crucial to conduct a thorough investigation to confirm whether the code smell signifies an actual issue that needs to be addressed. 

Why do code smells occur?

Most of the time, the issues in the codebase can be directly attributed to mistakes made by the programmer during the coding process. There are various reasons why this can happen, such as:

  • Poor design choices
  • Lack of understanding of software engineering principles 
  • Time restrictions
  • Lack of experience
  • Evolving requirements
  • Incomplete or inaccurate project documentation

The good thing is, that as with the actual smell, most often it is not so difficult to recognize. 

When a code smell is detected, there are several possible responses. 

The first option is to simply leave it alone and take no action. However, this can put organizations at risk for code rot and the accumulation of technical debt. Code rot refers to the deterioration of code quality over time, which can lead to decreased productivity and increased maintenance efforts. Technical debt, on the other hand, is the result of taking shortcuts or making compromises during the development process, which can lead to increased complexity and difficulty in making future changes.

The next option is to investigate the code smell instead of ignoring it. This involves taking a closer look to understand the underlying cause and potential impact. After investigation, a conscious decision can be made whether to address the “smell”. There may be cases where fixing the code smell is not feasible due to time or resource constraints. It’s also possible that the code smell does not indicate a true problem and can be safely ignored.

However, if your investigation shows that the problem must be addressed to eliminate the possibility of code rut or other problems, the most effective option is refactoring. Refactoring is the process of restructuring code to improve its design and eliminate code smells. It involves making changes to the code without altering its functionality, with the goal of improving readability, maintainability, and performance. Refactoring is the primary way to address problematic code smells and improve code quality.

How to identify code smells?

So, how to identify the presence of a bad code smell? Of course, we cannot actually sniff it, but luckily there are some effective methods to detect it.

Code review

One of the most effective ways to identify the possible problem is through code reviews. Code reviews involve a thorough examination of the codebase by other developers or peers. During the review process, reviewers can spot potential code smells by analyzing the code structure, naming conventions, complexity, and adherence to coding standards.

This method offers the advantage of having multiple sets of eyes on the code, which increases the chances of identifying code smells that might have been overlooked by the original developer. Additionally, reviews provide an opportunity for knowledge sharing and learning from others’ experiences, contributing to overall code quality improvement.

Automated analysis tools

Automated analysis tools, such as linters and static code analyzers, can be invaluable in detecting code smells. These tools analyze the codebase and flag potential issues based on predefined rules and best practices. They can spot a wide range of code smells, including duplicated code, overly complex methods or classes, and violations of coding standards.

The benefit of using automated code analysis tools is that they can quickly scan large codebases, which is quite difficult to do manually. They provide instant feedback and can be integrated into the development workflow, ensuring continuous quality monitoring. However, it’s important to note that automated tools cannot catch all code smells, and human analysis is still necessary.

Experience-based knowledge

Experience-based knowledge plays a crucial role in identifying code smells. Experienced developers who have worked extensively with different codebases and projects can quickly recognize patterns or code structures that have proven to be problematic in the past.

By leveraging their experience, these developers can identify code smells that might not be explicitly defined in coding guidelines or detected by automated tools. They can also provide valuable insights and recommendations for refactoring or improving the code to eliminate the issue.

Common types of code smells

Different projects and developers may have varying standards and expectations for code quality, so code smells are a common occurrence in software development. However, there are some widely recognized types of code smells that you can learn about to minimize their occurrence in your own code:


Bloaters refer to code smells that make the codebase unnecessarily large and complex. These include: 

  • Long Methods
  • Large Class
  • Data Clumps
  • Long Parameter List
  • Primitive Obsession

Bloaters not only make the code harder to understand and maintain, but also increase the risk of introducing errors. For example, a long method may be difficult to comprehend and debug, thus leading to a higher chance of issues.

To address bloaters, it’s better to create smaller and more focused methods and classes. Breaking down complex logic into smaller components not only improves code readability, but also makes it easier to test and maintain the code.

Change Preventers

Change preventers hinder the ability to make changes to the codebase easily, making it difficult to implement new features or modify existing ones without affecting other parts of the system. For instance, if a change in one class requires modifications in multiple other classes, it indicates a design flaw.

Change preventers include: 

  • Divergent Change
  • Shotgun Surgery
  • Parallel Inheritance Hierarchies

To mitigate this type of code smell, developers should adhere to the SOLID principles and design patterns that promote loose coupling and high cohesion. By decoupling classes and modules, changes can be made independently, reducing the risk of unintended side effects.


Couplers are code smells that exhibit tight coupling between classes or modules. Tight coupling means that the code relies heavily on the internal details of other components, making them difficult to replace or test in isolation. Examples of couplers include: 

  • Feature Envy
  • Inappropriate Intimacy
  • Message Chains
  • Middle Man

Object-Orientation Abusers

Object-orientation abusers are code smells that violate the principles and concepts of object-oriented programming (OOP). Examples include :

  • Switch Statements
  • Refused Bequest
  • Alternative Classes w/ Different Interfaces
  • Temporary Field

To avoid object-orientation abusers, developers should follow the SOLID principles and design patterns that promote clean and modular code. Each class should have a single responsibility, and dependencies should be explicitly defined and injected.


Dispensables indicate redundant or unnecessary code. They can clutter the codebase and make it harder to understand. Some common types of dispensable are:

  • Lazy Class
  • Comments
  • Speculative Generality
  • Data Class
  • Dead code
  • Duplicated Code

Best practices to reduce the code smell

To ensure clean and maintainable code, developers should actively work towards reducing code smell. Preventing it is an ongoing process that requires continuous effort and collaboration within your development team. There are some common practices that will help you reduce the code smell:


One of the fundamental practices to reduce code smell is proper documentation. Well-documented code is easier to understand and maintain both for the original developer and for future developers who may need to work on the codebase. It also helps prevent the introduction of code smell due to misunderstandings or misinterpretations of past code.

Documentation should include clear explanations of the code’s purpose, its inputs, and outputs, as well as any assumptions or limitations. It is also helpful to document the rationale behind certain design decisions or any known issues or workarounds.


Refactoring focuses on improving the structure, readability, and maintainability of existing code without altering its behavior. Its primary purpose is not to add new features. If you modify the behavior of a code segment during the process, it is no longer considered refactoring.

Overall, refactoring helps to:

  • Improve readability. By eliminating code smells, refactoring improves the readability of the codebase. Well-structured code is easier to understand, reducing the time and effort required for future modifications.
  • Enhance maintainability. Refactoring makes the codebase more maintainable by simplifying complex logic, reducing duplication, and improving the overall structure. This allows developers to make changes more easily without introducing new errors.
  • Improve collaboration. Clean code resulting from refactoring is easier to share and collaborate on. It allows team members to work more effectively together, as they can understand and modify the codebase with ease.
  • Increase efficiency. Refactoring helps optimize code performance by eliminating redundant or inefficient code. This can lead to faster execution times, reduced memory consumption, and improved overall system performance.

Continuous integration and continuous deployment (CI/CD)

Continuous integration and continuous deployment (CI/CD) empower DevOps teams to track and manage small code changes efficiently. CI/CD practices not only enable quick and efficient software development but also contribute to maintaining code quality by eliminating code smells and reducing the occurrence of manual errors. With CI, any modifications made to the code by individual developers are promptly recorded, bundled, and tested. This process helps eliminate the potential for code smells to arise. By implementing continuous integration, development teams can receive faster and more frequent feedback, resulting in fewer errors and improved software quality.

Additionally, continuous deployment automates the release of code changes and updates, reducing the likelihood of manual errors that can introduce code smells. 

Consistent naming conventions

Consistent naming conventions refer to the practice of using standardized and consistent names for variables, functions, classes, and other elements in a codebase. It involves following a set of agreed-upon rules and conventions for naming, which helps improve code readability

Here are some key principles of consistent naming conventions:

  • Descriptive and meaningful names. Use names that accurately describe the purpose or functionality of the element. This helps other developers understand the code’s intent without needing to dive into the implementation details.
  • Avoid abbreviations and acronyms. Unless widely understood and accepted in the domain, it’s generally better to avoid excessive abbreviations or acronyms in names. Clear and explicit names enhance code readability and reduce the chances of misinterpretation.
  • Consistency within the codebase. Ensure that naming conventions are applied consistently throughout the entire codebase. This includes maintaining consistent naming styles for variables, functions, classes, and any other elements across different files and modules.
  • Follow language-specific conventions. Different programming languages may have their own established naming conventions. It’s important to adhere to these conventions to ensure code consistency within the language’s ecosystem.

When everyone follows the same naming conventions, it promotes collaboration and reduces confusion, ultimately leading to more efficient and effective software development.

Expert Opinion

Understanding code smell, in my opinion, is primarily about the experience. It’s about grasping which solutions are sufficient in certain circumstances and which ones will cause problems in the future. Sometimes, within tight deadlines, you realize that the first solution that comes to mind already “smells” bad. And from experience, I know that it’s better to let that solution sit for 1-2 hours, and in the end, a new resolution will emerge that is not only implemented faster but also avoids future problems. 

The same goes for refactoring. An engineer should understand that not everything needs to be done canonically, according to textbooks. It’s always necessary to find the right level. Overengineering is the flip side of code smell, and the best solutions, as it is known, lie somewhere in between.

Pavel Vilbik, iOS developer at SoftTeco

Expert Opinion

For sure, following the best practices and keeping the code clean makes a developer’s life much easier. For instance, you can easily avoid typical issues and bugs if there are no “code smells” in your project. Moreover, it makes your code more flexible, scalable, and maintainable.

Of course, the above bits of advice are not universal for 100% of languages and technologies, but there are always trade-offs on how to make something elegant and robust at the same time without writing bad code. And the good news is that there are tons of “helpers” that can assist you to write great code: from public posts and discussions on the web to built-in mechanisms in your IDE.

Aleksandr Zvonik, Android developer at SoftTeco

Expert Opinion

If you prioritize code quality from the start, it becomes much easier to maintain it clean. The growth of technical debt/code smell is like taking out loans from a bank – with each new one, it becomes harder to repay, and eventually, the payment becomes unaffordable. It’s not solely the responsibility of one person but the entire team.

On the other hand, when the code is clean, tasks are completed more efficiently and smoothly. The business is satisfied, and we don’t experience much trouble while working with legacy code.

Artyom Parfenenkov, FullStack developer at SoftTeco

In conclusion 

Although code smells themselves may not directly cause the code to break, it is indeed crucial to be mindful of their presence. It can serve as warning signs that something could be wrong in the code, indicating potential issues or weaknesses. 

Addressing code smells may require some additional time and effort initially, especially when making changes or adding new features. However, by taking the time to address these issues, you will ultimately end up with code that is more robust, less complex, and easier to maintain in the future. This investment in code quality will surely pay off.


What is a code smell?

Code smell refers to certain patterns or characteristics in code that can indicate potential issues or weaknesses. It is a metaphor used to describe code that is poorly designed, hard to understand, or likely to contain errors. Just as unpleasant odors alert us to potential problems in the real world, code smells serve as warning signs for potential bugs, maintainability issues, and inefficiencies in the codebase.

Why should developers care about code smells?

Code smells are not just cosmetic issues. They can have a significant impact on the quality and maintainability of the codebase. Ignoring these “smells” can lead to a codebase that becomes harder to understand, modify, and debug over time. It can also increase the likelihood of introducing errors and decrease the overall productivity of the development team. 

Why are switch statements considered a code smell?

Switch statements often involve multiple branches and conditions, which can make the code complex and difficult to follow. As the number of cases increases, the switch statement can become convoluted and tangled, making it harder to reason about the code’s behavior. Besides, when a switch statement is used, it typically handles multiple cases or behaviors within a single function or method, making it more likely to violate the SRP principle.

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